The diagnosis of nervous diseases.

  • Purves-Stewart, James, Sir.
Date:
1906
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Licence: In copyright

Credit: The diagnosis of nervous diseases. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    fibres in the medulla, pons, and so on, to the perceiving centre in the cortex. Moreover, a discharge of motor energy from the motor cell in the anterior cornu can be produced not only reflexly, from below, but also voluntarily, from above. This is acMeved by an impulse descending from the cortical motor centre of the opposite side, through the crossed pyramidal tract down the cord to the anterior cornual cell (see Fig. 2). A discharge can also be voluntarily inhibited from above. Confining ourselves now to the consideration of a cerebro-spinal reflex motor action, we must bear in mind that afferent impulses, on reaching the cortical sensory centres, do not necessarily produce a descending impulse along the pyramidal tract. If they do, this is simply an automatic action, or a longer variety of reflex. There exist in the cortex perceiving-centres which take cognisance of the source and nature of the stimulus, and determine whether or not any i Voluntary Motor fibre Muscle Fig. 2.—Diagram of a Voluntary Motor Act. Skirv